The flat bar torsion spring suspension assembly of the present invention is of the same general type as disclosed in Bainbridge U.S. Pat. No. 2,977,132, and like the Bainbridge suspension assembly, the assembly of the present invention provides a resilient means for securing the wheels of a trailer, or other vehicle, to the frame. However, the arrangement described in the Bainbridge patent is more complex and expensive to produce in volume than the assembly of the present invention, and it does not encase the suspension assembly into a housing which simplifies attachment to a frame and permits incorporation into a frame and a housing acts to protect the working parts from the elements, as is the case with the embodiments of the invention to be described in the following specification.
The assembly of the present invention is also advantageous over Bainbridge, in that the torsion bar is held in corresponding sockets without holes and bolts. The absence of holes in the torsion bar reduces stress risers and decreases manufacturing costs significantly. It is also then much simpler to configure the socket to receive one, two or more torsion bars thereby adjusting the spring rate.
The suspension assembly of the invention is also advasntageous in that is provides for the wheels at each side of the vehicle to be individually suspended, so that torsion bar configurations of different strengths may be used, if so desired, for the different wheels of the vehicle as a function of the load distribution. Because independent suspension assemblies are provided on each side of the frame of the vehicle, the frame width may be easily varied by changing the length of a center connector. Additional assemblies can also be easily added in tandem or triplex by simply adding a frame rail between assemblies in the lengthwise direction. This is in contrast to the current requirement for an entirely new system and in contrast to the Bainbridge patent which would require additional frame considerations.
An important feature of the suspension assembly of the invention is that it is simple and inexpensive in its construction, and it may be manufactured simply and easily, and assembled and mounted on a vehicle with a minimum of effort. Furthermore, since the housing for the suspension assembly, in the embodiment to be described, can double as the frame for the vehicle, the overall resultant weight requirements of the vehicle may be reduced with a subsequent reduction in moment of inertia, which is highly desirable for trailer stability.
To reiterate, the suspension assembly of the invention is advantageous over the prior art assemblies in that it is simple in its design, and in that it is relatively easy and inexpensive to manufacture; in that the housing is designed in and with the suspension making them an integral part capable of being moved as a unit; in that its width is adjustable to accommodate different vehicle frame configurations; in that the housing may become integral with existing vehicle frames, or bolted onto existing frames if so desired, with no elaborate borate mounting structure or separate framework being required; and in that the heat treated flat torsion bar is mounted in the assembly without holes which reduces stress concentrations and decreases production costs.
As described above, the suspension assembly of the invention may be manufactured with the entire assembly housed inside and protected by the framework of the trailer housing. Since the housing can then double as the framework of the trailer, the trailer itself may then be designed around the suspension assembly so that it may be easily assembled and disassembled. This permits the trailer to be carried to the loading site in a disassembled state on the towing vehicle, and to be assembled with a minimum of effort at the loading site.